Process of obtaining purified ammonia from coal-gas.



G. G. TUPTS.

APPLICATION FILED HAY 18, 1911.

Patented June 24, 1913.

lunfyqywoz s PROCESS or OBTAINING PURIPIED AMMONIA PROM coAL GAS.

a preliminary scrubbing in tar :to remove the tar carried in suspensionin the gas (and, if desired, .after such cooling as is possible withoutcondensation of the water vapor, as -by .passi-ng them through a tubularsTATEs PATENT oir-Frou.

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speciliqmon maken f awnmnaienhyiauu. 'semimzspea- Patented June '24,1913.

To allwmitmageon'm: y

Bev it 'known 'that I, G. Tum, .a

of4 United States, residing-atse, im the county of and Stateef-iNevYork, have inventada new .md Impmvedmcess 'of @bmi-ning Puri edAmmonia from Coal-Gas, of which the following' vis a specification;

VM 'vnvention relates particularly to the porigication 'olf ammonia asit is obtainedin the destructive distilation of coa-l.

As is wel-l known, ammonia -derive'd from thisnsource is as it comesfrom the oven or retort, associated with many impurities, such as tar'land ta'rry compounds, pyridin and pyr'idiln oils, alcohol compounds,nitriles, and many other vvolatile organic and 'nf'rorganric compounds.Heretoore these have lbeen separated from ltheammonia 'by cooling andvWashingfth'e gases of distillationl whereby in the tirst instance,so-c'alled ammoniacalliquor is reduced., which lcontains the laimnonia.an 1 the impurities, and which afterward treated in various, generallycomplex and tedious, ways to rccover the ammonia 'freed gfro'r'n 'theimpurities. My process, on'the contrary, isdirected to the directtreat-ment fof the ovengases to the end of recovering Ipurified ammoniawithout the preliminary steps o'f washing and forming am'moniacallliquor, with the result of great simplicity and economy -both inmanipulation and in the apparatus requi-red. i

In the accompanying drawing I have indicated diagrammatically y aconventional form o`f1apparaftus which may be employed in carrying myinvention in to effect, -eacll of the separate'parts of which is old andwell kfnown.

In carrying my process into eiect I talce the .gases of distillation asthey come fromV the oven main and, either with or wit-hout condenser)cause them to pass through a saturator containing sulfuric acid or acidsulfate of ammonia.A y

The ammonia compounds of the gas are broken up in the saturator, theammonia combining with the -acid to form ammonium sulfate. Among theseare included the fixed ammonia compounds, such as ammonium chlorid,` forthe recovery of the ammonia content of which 'the lime treatmenthash'erctooe beenl essential. AThe acid radicals of these pass o withthe uncombined ases, the vammonia combining With the acidin thesat-mater. In this respect my process presents a material advantage,especiaily in the treatment of those gases` which aconsidv era'bleroportion ofthe ammonia is present in the orm of fixed salts, since thenecessity of -u'sing lime to effect the decomposition of these isentirely obviated. The bul-k of the gases of distillation, which may. befdesignated as coal gas, passes off from the satui rater and may beburnedunder boilers, or treated 4in -anydesired manner and stored foruse. Certain other gases which are usually present in ammoniacal liquor,either uncombined or in't'he form of unstable compounds of ammonia, suchas'CO2 and HZS, and which constitute a large, part of the bulk of theimpurities from which the lammonia requires to be freed, are dissociatedfrom the ammonia at this point and pass .off with the coal gas. With thecoal gasthere will also fpass oli' 'from the saiturator certain of thelight oils present, such as benz'ol, toluol a/nd x'ylol, and, in casethe tar has not been previously removed from the gas, a'portiori of thetar. The remainder of the tar will remain in the saturator mixed withthe ammonium sulfate formed therein.'

The ammonium sulfate formed is then removed from the saturator and driedas by being allowed to settle in a sludge tub and then passed through acentrifugal drier, the drainings in each case being returned to thesaturator, and is then conductedl to a kiln' where it is brought asquickly as possible to atemperature suiiiciently high to decompose theammonium sulfate, care being taken to avoid the decomposition ofammonia. That is, Ethe temperature should range from 350 C to notexceeding 400, C.

The nitrogenous Vorganic and carbon compounds accompanying the ammoniaas impurities, though some port-ion of these may be oxidized and remaininthe kiln, are. in the main volatilized and driven off with ammoniadissociated from the ammonium sulfate, which is converted into acidammonium sulfate` with some pyro sulfate of afnmonia, in case thetemperature has been' carried to near the higher limit permissible.

'foi

Such tar as has remained with the ammonium sulfate is either convertedinto pitch or charred and is removed rfrom the liln with the acidammonium sulfate to a dissolving tank. The acid ammonium sulfate isdissolved to be subsequently returned to the saturator to be again usedin the for mation of ammonium sulfate. The pitch, tar and otheraccompanying impurities settle or float in the tank and are easilyseparated from the solution, as by decantaton, filtration, or skimming.

The` gases driven off from the kiln, z'. e., the ammonia with theaccompanying impurities, are then cooled, as by being passed through atubular condenser, to such low point, say 20 to 25 C., as willfacilitate tlie subsequent purification, andl the final purication isthen effected inany suitable manner, as by passing the mixed gasesthrough a cold/ammonia purifier, consisting of superposed pans forming astack or Wash column and containing a saturated solution of ammonia inwater maintained at a low temperature by the circulation of a coolingliquid. The construction and operation of such a purifier isfullydescribed in L-etters Patent obtained by me, jointly with others, No.1,012,272, Dec. 19, 1911. and need not be further described herein. Init the impurities accompanying the ammonia are absorbed and held by thesaturated solution 0f ammonia while the pure ammonia gas passes, or isdrawn, off to be absorbed in an absorber to form aqua ammonia, or to betreated as may sbe desired.

The advantages of my process will be obvious to these skilled in the artsince it grtatly simplifies the recovery of the ammonia in a pure stateby dispensing with the washing of the gas to form ammoniacal liquor andthe subsequent distillation of the liquor, together with the complicatedand expensive apparatus incident thereto, and

also entirely obviates the necessity of using` lime to break up thefixed ammonia compounds.

What I claim as new and desire to secure by Letters Patent is:-

1. The hereinbefore described process of recovering purified ammoniafrom the gases obtained from the distillation of coal which consists infirst treating .the mixed gases as they come from the retort to separatethe tar therefrom, then passing the gases through acid to form ammoniumsulfate,

drawing ofi the uncombined gases and leaving the ammonia with the:remaining umpurities in the sulfate; heating the ammonium sulfate so asto drive ofi` ammonia in company with the volatilizable impurities andfinally'separating the ammonia from the impurities.

2. The hereinbefore described process of recovering purified ammoniafrom the gases obtained from the distillation of coal which consists intreating the mixed gases as they come from the retort with acid so thatthe fixed ammonia compounds are`broken up and ammonium sulfate isformed; drawing ofi1 the uncombined gases and leaving the ammoniatogether with the remaining impuritiesin the sulfate; rapidly raisingthe ammonium sulfate to such temperature as to volatilize ammoniaandvolatile impurities and drawing ofi' the volatilized productstogether and finally separating the lvolatilized ammonia from theaccompanying volatilized impurities.

3. The hereinbefore described improvement in the art of recoveringpurified ammonia from coal gas which consists in passing the gas asproduced through acid to form ammonium sulfate, quickly heating theammonium sulfate so as to drive ofi'l ammonia with accompanyingimpurities, and leave acid ammonium sulfate, forming a solution of theresidual acid sulfate and recharging the solution with ammonia to formammonium sulfate in the same manner as before to repeat the operation.`K

4. The hereinbefore described improvement in the art of recoveringpurified ammonia from coal gases lwhich consists in passing the gas asproduced through acid whereby ammonium sulfate is formed; heating theammonium sulfate in such manner as to volatilize ammonia contenttogether with the volatileJ impurities and to leave behind the tar inthe shape of pitch and charred product, withdrawing the volatilizedammonia with the volatilized impurities and finally separating theammonia from the impurities.

In testimony whereof, I have hereunto subscribed my name, this 9th dayof May CHARLES G. TUFTS.

Witnesses:

HERBERT N. COLE, H. DUANE BRUCE.

